The present invention relates to a lip seal device for water pumps.
Heretofore, for sealing the water pump of an automobile, a mechanical seal device has been used. Generally, such devices include a follower ring slidably and axially provided within a case attached to a housing, and a sealing plate mounted on a rotary shaft passing through the shaft of the follower ring with the follower ring being brought into sliding contact with the sealing plate due to the elastic force of a coil spring, whereby the engine coolant is kept liquid-tight by the sealing surface between these members. An example of such a mechanical seal is shown in commonly assigned U.S. Pat. No. 4,733,873.
However, the mechanical seal device of the above structure has disadvantages in that since the follower ring is supported by the coil spring, it has a wide range of freedom of movement so that it can easily frictionally vibrate. Once the follower ring has begun to vibrate, the coil spring also vibrates in resonance therewith, resulting in transmitting an amplified vibration to all parts of the automobile engine. This phenomenon is especially bothersome when the engine is at idle or rotating at a low speed, that is, when the engine noise level is low. During such times, an abnormal "creaking" sound is liable to be heard.
Further disadvantages of the mechanical seal device are that since the follower ring is slidably mounted in the case so as to come into sliding contact with the sealing plate due to the elastic force of the coil spring, not only is the overall seal device unavoidably large, but also the structure thereof is complicated and expensive.
Further, a lip-type seal device is known for use in sealing an automotive compressor which uses no coil spring. An example of such a lip-type seal device is described in commonly assigned U.S. Pat. No. 4,721,314. However, such seal devices have not previously been used for sealing water pumps. That is, in a compressor, the liquid for which the seal is provided is a type of oil, which provides a much better lubricating effect for the seal than can water in the case of a water pump. If such a lip seal for a compressor were used in a water pump, leakage would unavoidably occur.